Today may go down as one of the most important days in the history of science, and possibly in the history of mankind. Today it was announced that a planet was discovered orbiting Proxima Centauri, the nearest star to our solar system. Not only is this planet close to us by astronomical standards, but it is also earth-sized and orbiting in the habitable zone of its star, raising the possibility that this planet may harbor life! Many other websites have news stories about this discovery, so I’m going to try to provide a little more perspective and analysis on this based on my background in astronomy.
How Do We Know About This Planet?
Astronomers have known that Proxima Centauri is the nearest star to us since the early 20th Century. It is part of a triple star system that includes Alpha Centauri A and B (two yellow sun-like stars that orbit each other) with Proxima Centauri being a very small, faint, red star in a wide orbit that goes around both Alpha Centauri A and B. Proxima Centauri is 4.25 light years away while the Alpha Centauri double stars are slightly further away at 4.37 light years. Being the nearest stars to us they have been the subject of lots of astronomical scrutiny, but despite this, no planets have previously been confirmed to orbit any of the stars in the system (though there have been a number of false alarms in the past). Planets are very small in relation to their parent stars, and they are also very faint, so detecting any planet, even around the nearest stars is very difficult. The planet around Proxima Centauri was not seen directly but instead was inferred from the motion of Proxima Centauri. By observing Proxima with a very sensitive spectrograph (an instrument that splits up light into a rainbow of colors) the velocity of Proxima either towards or away from the Earth was able to be measured. A planet, although small, has gravity, and pulls on its parent star. This pull shows up as a back and forth shift in the velocity of the parent star as the planet orbits around it. Without a planet you’d see no velocity shift. With a planet you see an incredibly small velocity shift that, nonetheless, a sensitive spectrograph can measure. These measurements are at the very limits of what our technology can detect, but technology keeps getting better. By assuming that physics works the same at Proxima Centauri as it does on the Earth we can use our knowledge of physics to infer what kind of planet it would take to create the observed velocity shifts we see. That’s how we know that this planet is at least 1.3 times the mass of the Earth and orbits Proxima every 11.2 days. We also know how far away that means the planet is from its star. And then given what we know about the brightness of Proxima we know that the planet is in the so called Habitable Zone, the distance from a star where a planet would be neither too hot nor too cold for liquid water to persist. So this all seems really promising and it is possible there are aliens right now on this planet looking up at us.
Why is this Discovery Significant?
This is big news for a number of reasons. First it’s a new planet discovery which increases the number and types of planets we’re aware of and teaches us more about what types of planets are possible. But the real excitement lies in that this is the CLOSEST star to the Earth and the star that we’re most likely to visit first, either with a probe or with actual human astronauts. So we may have just discovered where the first footfalls on another star system will take place in the future. But it’s also significant in that this planet could be habitable and host life as we know it. This is particularly remarkable because Proxima is what’s known as a Red Dwarf star. Red Dwarfs are THE MOST COMMON stars in the entire universe, outnumbering all other types of stars combined. They have lifetimes of TRILLIONS of years whereas stars like our sun only last for a few BILLION. So there is plenty of time for life to develop. But the downsides are numerous including that Red Dwarfs are incredibly faint (Proxima is only 1/20000 as bright as the sun). Even being the closest star to the Earth, it is still too faint to be seen with the naked eye. If the sun is like a raging bonfire, big enough for dozens of people to be around and receive its warmth, then Proxima is like the dying embers of campfire where you have to press in close to get any warmth at all. So the fact that a planet was found close enough in to Proxima to potentially be warm enough for liquid water to exist is remarkable. There’s much we don’t know about Proxima’s new planet, including what it’s atmosphere is made of. But even in the best case, this planet might not be a great vacation spot. The planet is likely tidally locked, meaning it keeps one side pointed towards its star (similar to how the moon only points one side to us and we can’t see its “dark side” from Earth. So Proxima’s planet probably has a bright side where the sun always shines and a dark side which is bathed in perpetual darkness. What the temperature and weather is like on such a planet is unknown. It may be freezing cold on the night side and blazing hot on the light side, with a narrow zone in between where the temperatures may be just right for life. But we really don’t know. Also, Red Dwarfs are known to produce solar flares aplenty. A tidally locked planet probably doesn’t generate a magnetic field which helps to shield the atmosphere from solar flares. Over time, the atmosphere of Proxima’s planet may have gotten blasted away by continual solar flares, leaving behind an airless rock in space. But, again, we really don’t know. There could also be other planets orbiting Proxima (it would be strange if there was just a single planet around a star) and those planets could have even more unusual properties and interactions. And we really don’t know that much about the habitability of planets either. We now think there is an ocean of liquid water under the ice of some of Jupiter’s moons, even though Jupiter is way too far from the sun to get enough heat to expect there to be liquid water. Ultimately, this discovery may be most important because it’ll catalyze more research into discovering other planets around both Alpha and Proxima Centauri and push the technology needed to discover even more planets around other stars.
How Soon Can We Go There?
This discovery may also be important in galvanizing efforts to figure out how to send a probe or humans to another star system. In the near term we can learn more by developing better telescopes and instruments. The James Webb Space Telescope will be launched in a few years and will be able to study planets around nearby stars. And there is a new generation of very large ground based telescopes that will be built in the next few years. Discoveries such as the planet around Proxima Centauri will give justification for even more sensitive planet hunting instruments for these telescopes. In the near term we should be able to learn a lot more about these planets and might even be able to detect the chemical signatures of life on them. If we exhaust what we can learn from the Earth and actually want to send a space probe to Proxima Centauri, we have to confront the fact that even the closest star is an extremely long distance away. The fastest space probe we’ve made is New Horizons, which took 9 years to travel to Pluto. At that same speed, it would take 62,000 years to get to Proxima Centauri. In fact, most space is empty and the region around a star that constitutes its solar system is miniscule. If our sun is like a porch light and the planets are like a swarm of moths hovering within a foot of the light, then the next nearest star is like another porch light a mile and a half away, with nothing but dark space in between. To get to the nearest stars in anything like a human lifetime, we’d need to figure out how to travel faster. Science fiction frequently invokes warp drive and other faster than light travel. But the reality is our understanding of physics is insufficient to conceive of any credible faster than light transportation schemes. Traveling at a significant fraction of the speed of light is physically possible, but would require energies and masses that are far beyond what our species has been able to tap into thus far (even getting a probe the size of the Hubble Space Telescope moving at half the speed of light would take the accumulated power output of the entire human civilization for a period of several years). There is only one technology that we currently have access to, that we can reasonably say would work, and that could power an interstellar spaceship capable of making a trip to the nearest star in something close to a human lifetime. That technology is a Project Orion style nuclear pulse propulsion spaceship. It would be powered by the impulse provided by hundreds of thousands of exploding thermonuclear bombs. Such an interstellar spaceship would be mind-blowingly huge, wider than a sports stadium, and weighing hundreds of thousands of tons (for comparison, an aircraft carrier weighs about 100,000 tons). It would be the largest moving object ever created by man, let alone placed into space. The cost would be staggering, probably trillions of dollars. But technologically, it COULD work and could send people to the Alpha Centauri system in a journey lasting somewhere between 50 - 100 years. I’m not saying it’d be worth it, but who knows how we’d feel if we discover evidence of life around a nearby star. It might be the greatest inspiration for us as a species to invest in technology and science and could usher in an age of rapid progress and have ramifications we can’t currently imagine. Ultimately the appeal of space is that it forces us to expand our imagination into bigger and more wondrous possibilities.
The question I get asked the most is "what telescope should I buy?" This usually comes from friends who are not amateur astronomers but who have a general interest in astronomy or just think it would be cool to have a telescope. Many have kids and want to nurture their curiosity with the gift of a telescope. Unfortunately, the question of what telescope to buy is nearly as complex as asking what automobile one should buy. We live in a time when there are hundreds of telescopes on the market, and thousands of accessories for them. There is also a huge range in prices for telescopes from about $50 on the low end to upwards of $100,000 on the high end! Even within the sensible range of prices most consumers could afford, there are many types of telescopes to choose from and it can be hard to know the relative merits of 2 telescopes at the same price. So how can one make sense of this complexity and zero in on what is the best telescope to buy?
Hopefully this blog entry can give some good advice on this topic. While there is no one, single telescope that is better than all others, there are certain considerations that hold true and can inform someone’s decision on what telescope they should buy. Firstly, if you are an experienced amateur astronomer, you are probably already beyond the advice in this blog entry. Astronomers debate for hours the relative merits of a new apochromatic refractor or a Newtonian astrograph. There are several good forums, such as Cloudy Nights, that have a wealth of information and opinions on these topics. This blog entry is for the complete novice who is looking to buy their first telescope and is just getting started in astronomy.
My first plea is to never buy a cheap “department store” telescope. These are typically found in the toy section of common big box stores and cost $100 or less. These telescopes usually have plastic lenses and long tubes. They are marketed towards young kids and, being cheap, many parents gravitate towards them. The problem is they are too cheap. Image quality is poor, there is no clock drive to follow objects, and the telescopes tend to be small and limited in their light gathering power. You can’t see much with them and they are more an exercise in frustration. The average kid will fumble with the telescope for a few minutes, get frustrated because it’s too hard to use, and then abandon it forever. Why waste $100 on such a telescope when a few hundred dollars more will buy a telescope your child will actually use?
If you are pressed for money, I recommend buying a pair of binoculars instead. A decent pair can be purchased for about the same cost as a “department store” telescope and is much more useful. For instance, binoculars can be used for daytime viewing such as sports events and birdwatching. Binoculars are specified by two numbers, their magnification and the size of their main lens. So a binocular specified as 10x50 has a magnification of 10 times and a main lens diameter (aperture) of 50mm. You might think the bigger aperture and higher magnification the better, and for enough money you can buy truly monstrous binoculars. However, bigger binoculars are heavier, and since you’ll be holding your binoculars while you scan the sky, your arms will get tired pretty quickly. On the other side, a too small pair of binoculars won’t gather much light and you won’t be able to see many astronomical objects. Similarly, higher magnification might sound better but it’ll make it that much harder to hold the binoculars steady enough to get a clear view. I have a pair of 16x50 binoculars and I can start to see that the magnification is getting high enough to make holding it steady a challenge. I’ve found that the best balance of magnification and aperture is about 10x50. A good 10x50 binocular can easily be had for less than $100, and maybe even less than $50. With such a pair you’ll easily be able to see brighter deep sky objects like the Orion Nebula and the Andromeda Galaxy as well as star clusters, the moon, and man-made satellites. Binoculars are intuitive, easy to use, and kids will love them.
If you or the person you’re buying for is ready to move beyond binoculars and wants to see more deep-sky objects, we’re back to the question of what telescope to buy. I suggest you are going to have to spend at least a few hundred dollars to get a decent telescope. The good news however is that the price of a decent telescope keeps coming down and the capabilities keep going up. I think an indispensable feature for any telescope is to have a motorized clock drive such that the telescope automatically follows an object as it moves across the sky. Astronomical objects, much like the sun, rise in the east and set in the west and move steadily across the sky. You might not think this is a big deal, but the small fields of view of most telescopes (after all telescopes magnify objects and this leads to small angular fields of view) means that the rotation of the Earth will, in just a few seconds, move objects out of your telescope’s field of view if you don’t have a clock drive. Also, if your telescope has the motors and gears needed for a clock drive, you’re halfway to what’s called a “Go-To” telescope. This feature utilizes a small computer in the telescope mount or hand-controller to allow the telescope to know where it is pointing and to be able to find and point to astronomical objects automatically. In the past, this feature was only in top-of-the-line telescopes costing thousands of dollars. Now it can be found in some of the cheapest telescopes costing just a few hundred dollars. And the advantage is profound, especially if you are new to astronomy and don’t know where many astronomical objects are or how to find them. With a Go-To telescope, you initially align the telescope by inputting your location, time, and date into the computerized hand-controller. Typically then the telescope will begin an alignment sequence whereby it points to a few bright stars to further refine its positioning. During this step you will have to know at least a little astronomy and be able to adjust the telescope’s initial “guess” and center up the bright alignment star in your telescope’s field of view. This alignment step literally takes just a few minutes, and once complete, you can point to any object in the telescope’s on-board database of thousands of objects without you having to be an expert on where it is located in the sky. Do you have no clue how to spot the Ring Nebula or the Hercules Globular Star Cluster? With a Go-To telescope, you just find the name of the object in the on-board menu and hit “Enter” and the telescope will automatically point to it. I’m old enough to remember the days before Go-To telescopes, where you had to remember the location of astronomical objects and little hints about how to find them. While that may have fostered a deeper connection with the sky, it did mean you spent more time trying to find objects than actually observing them. With a Go-To telescope, astronomy is more fun because you’ll have an easy time finding and observing astronomical objects.
So now we’ve concluded a telescope with a low cost Go-To mount and clock drive is best. But what about the actual type of telescope optics? There are two main categories of telescopes, “refractors” that use lenses and “reflectors” that use mirrors. Within these categories, there are tons of variations. Bigger telescopes like ones used by professional astronomers and advanced amateurs are almost all reflectors. They scale up better to larger sizes than refractors. That being said, I think the best type of telescope for someone starting out in astronomy is a refractor type telescope. Refractors are simple, lightweight, and don’t require you to adjust the alignment of the internal optics. Refractors are what people think about when you mention telescopes. A pirate’s spyglass and brass “harbor” telescopes are of the refractor type. They use lenses to gather light and focus it down a long tube to an eyepiece at the other end. Refractors, and indeed all telescopes, are specified by the size of their main light gathering optic (the aperture) and by their focal length. Much like with binoculars, bigger apertures gather more light, and longer focal lengths lead to greater magnification. Refractors tend to have their apertures specified in millimeters. Since you’ll have a mount for your telescope, the warning I gave about binocular apertures getting so big that your arms would get tired quickly doesn’t apply. But bigger apertures still lead to larger and more expensive telescopes, and with refractors, this trend grows quite quickly. A good sized amateur refractor is about 120 to 150 millimeters (about 5 to 6 inches). Going beyond that and the price climbs very quickly. I’ve seen 8-inch refractors before but they cost as much as a car, while an 8-inch reflector telescope can be had for less than $1000. So I recommend a refractor around 120 millimeters or less purely on cost grounds. Additionally, super long focal lengths (magnifications) sound nice but are not the way to go for a first telescope. For one thing, long focal lengths lead to long telescope tubes, which leads to heavier telescopes on heavier, more expensive mounts. Also, the field of view you’ll get will be smaller, and may challenge the accuracy of the Go-To mount to get astronomical objects in the middle of your telescope’s field of view. Finally, smaller focal lengths tend to smaller but brighter images, making it easier to see faint astronomical objects by eye. This all spells out what is called a “fast refractor”, that is a refractor type telescope with a relatively short focal length that is 5 to 7 times the size of the aperture. So for instance, a 120 millimeter fast refractor might have a focal length of 720 millimeters. With a standard 25 millimeter eyepiece, you’d get a magnification of about 29x, which will give nice views of larger astronomical objects like star clusters and the Orion Nebula. In comparison, our 10x50 binoculars only had a magnification of 10x, so we’re definitely going to see more detail with this telescope.
Great, so we’ve nearly narrowed down on the “ideal” first telescope. It would be a fast refractor type telescope with an aperture less than 150 millimeters, on a computerized Go-To mount that allows you to automatically point to and track astronomical objects. I haven’t talked about price too much yet but have implied that the reader is price conscious and maybe doesn’t want to spend a ton of money on a hobby they are not yet sure about. The good news is that an ideal first telescope can be had for a little more than $400. I don’t want to endorse any particular telescope, but some examples of telescopes that fit our requirements include the SmartStar R80 Computerized Telescope with GPS from Ioptron ($370). This is a Go-To mount with an refractor telescope with an 80mm aperture. The mount has built in GPS so the telescope always knows its location. Another possibility is the Nexstar 102 SLT Computerized Telescope from Celestron for $499.95. This has a fast refractor with 102 millimeters of aperture and a 660 millimeter focal length. Another exciting possibility is the Astro Fi 90mm Refractor Telescope also from Celestron. This telescope is soon to be released so we don’t know how good it is, but it will be controllable via a WiFi connection to a smartphone or tablet, and the price will be an affordable $399.95. There are a few other possibilities, but I'll leave it up to the reader to investigate some more to find a good fast refractor telescope within your budget. Paying more money should get you a nicer telescope, so if you can afford it, you can look to at greater than $500 telescopes, of which there are many. Some good online vendors of telescopes include:
Good luck and clear skies!
Astronomy Labs has recently debuted a 2-inch version of the starsplitter. It works in the same way as the smaller 1.25-inch version, but is better suited to astrophotography. It accepts 2-inch accessories including eyepieces and cameras, and, with adapters, can be used with 1.25-inch accessories as well. The great advantage of this comes when doing astrophotography. Having two identical output ports means you can autoguide your exposures with the same optical path that you image with. Your autoguider will be at the same focal length as your main camera and will be more sensitive to tracking errors than if mounted on a separate guidescope. Flexure between a separate guidescope and the main scope is also eliminated. The results are striking. The image below and on the left shows a 10 minute exposure that was autoguided with a separate guidescope. Mis-tracking on the exposure is profound. This is a ruined and unusable exposure. The image below right was taken right after the first but with the autoguider on the 2nd port of a 2-inch starsplitter. The exposure was also 10 minutes long but the guiding is much better. The star images are nice and round and the image is of good quality.
A lunar eclipse is a spectacular event, one that you might want to share with family and friends and also shoot photos of. If you only have one telescope, this could be a challenge. You wouldn't ordinarily be able to do both at the same time. With a StarSplitter, however, you get two outputs from one telescope. I used this feature to livestream the eclipse with a video camera on one StarSplitter port and use the other port to mount a digital SLR camera. The two cameras have different back focus distances, so I used a barlow lens on the digital camera port in order to reach focus. The pictures of the setup are below. The recording of the livestream is on the Astronomy Labs Youtube page and a timelapse made from the photos taken by the digital camera can be viewed below.
The StarSplitter Accessory is compatible with Digital SLR cameras. In order to interface to the StarSplitter's 1.25-inch output ports, you'll need a T-thread adapter for your digital SLR camera. Most will already have this as you need one in order to attach your DSLR to a telescope at all. In addition you'll need a 1.25 inch to T-thread adapter. This will go between the StarSplitter output port and the Digital SLR T-thread adapter. The next issue you'll encounter is that Digital SLR cameras require more backfocus distance than most other accessories. If you want the other StarSplitter port to be in focus at the same time, you'll need to extend that port's backfocus distance to match the DSLR's. This can be accomplished by adding an eyepiece extension tube. These are sold by most astronomy stores and extends how far back the eyepiece or accessory attaches by about 2 inches. Different lengths may be available. Once installed your StarSplitter should look like the pictures below and you should be able to achieve focus with a DSLR camera and an eyepiece or autoguider at the same time.
The April 2014 lunar eclipse provided a great opportunity to showcase the StarSplitter. It is capable of being used with digital SLR cameras. This image was taken with a Canon T2i camera.
On Thanksgiving Day comet ISON had its closest approach to the sun. Early reports indicate that ISON did not survive and either broke up or simply melted away. However, as of this morning (the 29th) what happened is not entirely clear and comet ISON may, in fact, have survived. We'll probably know for sure within a day or so. S
I have been excited about space since I was young, and have been involved in astronomy for over 20 years. I have built 4 of my own telescopes and continue to design and experiment with new instruments and accessories.