APOD: Proxima Centauri: The Closest Star (2016 Jan 18)

[Nitpicker]

I suppose the list of brightest stars is based on what is resolvable by the unaided eye. So, Alpha Cen is considered brighter than Arcturus.

[JMac]

With our current knowledge we just might be able to make a small vehicle that could reach something like 10% of the speed of light over that sort of distance, and assuming constant acceleration and no braking at the other end (kind of like the recent Pluto mission), that makes for an average speed of 5%, or 1/20th of light speed. So for such a vehicle to reach Proxima Centauri, at 4.24 ly distance, it would take about 20 x 4.24 = 84.8 years. It would then take a further 4.24 years for the pictures to get back here, for a total of about 89 years from launch. Note that the above is wildly optimistic. Although the theory of how such a ship would operate is understood, no one has ever tried to build one.

It would probably be beyond our current capability. It would not be small, and it would cost more than any other public project ever funded. We don't know how to shield a craft at 0.1c from the kinetic impact of space dust. We don't even know how to make electronics that can reliably survive for 100 years (solid state chips grow internal shorts and fail in decades).

Realistically, this is beyond our means.

True dat, Chris, but I worked out the space dust erosion factor years ago. Briefly, the craft's outermost skin would be made of regenerative ice. With erosion recovery, filtration & re-application, a closed system reducing initial load needs, possibly even bolstered by living payload energy emissions would be possible.

[Cousin Ricky]

I suppose the list of brightest stars is based on what is resolvable by the unaided eye. So, Alpha Cen is considered brighter than Arcturus.

The explanation referred specifically to “the brightest star in the Alpha Centauri system.”

[neufer]

I suppose the list of brightest stars is based on what is resolvable by the unaided eye.
So, Alpha Cen is considered brighter than Arcturus.

The explanation referred specifically to “the brightest star in the Alpha Centauri system.”

This is a list of the brightest naked eye stars, as determined by their maximum, total or combined apparent visual magnitudes as seen from Earth. Although several of the brightest stars are also known close binary or multiple star systems, they do appear to the naked eye as single stars.

Code: Select all

Bayer     Proper name                            V Mag.class
------------------------------------------------------------------
α CMa     Sirius                                  −1.46
α Car     Canopus                                 −0.74
α Cen AB  Rigil Kent                              −0.27 : (0.01 [+] 1.33) 
α Boo     Arcturus                                −0.05
α Lyr     Vega                                     0.03
............................................................
ε Ori     Alnilam                                  1.69
γ Vel     Suhail, Regor*                           1.72 : (1.84 [+] 4.27)
α Gru     Alnair                                   1.74
ε UMa     Alioth                                   1.77
ζ Ori     Alnitak                                  1.77
α UMa     Dubhe                                    1.79
α Per     Mirfak                                   1.80 
δ CMa     Wezen                                    1.82
θ Sco 	 Sargas 	                               1.84

*The name Regor ("Roger" spelled in reverse) was invented as a practical joke by the Apollo 1 astronaut Gus Grissom for his fellow astronaut Roger Chaffee.

<<In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope.

There are three types of paired stars:

• optical doubles—unrelated stars that appear close together through chance alignment with Earth
  
  visual binaries—gravitationally-bound stars that are separately visible with a telescope
  
  non-visual binaries—stars whose binary status was deduced through more esoteric means such as occultation (eclipsing binaries), spectroscopy (spectroscopic binaries), or anomalies in proper motion (astrometric binaries).

Conceptually, there is no difference between the latter two categories, and improvements in telescopes can shift previously non-visual binaries into the visual class, as happened with Polaris in 2006. Thus it is only the inability to observe the third group telescopically that makes the difference.

[Ann]

If a star gives good evidence for close-up investigation, journeying there will need to be planned exquisitely with respect to where it will be. (As Art pointed out)

Click to view full size image

Good point, Ron!

Michael J. Fox, if you had a time machine that sent you back in time without sending you to the exact right point in space in the direction of Carina quite far away from "here", you would end up in empty space and freeze all the body parts off your body.

Ann

[Ron-Astro Pharmacist]

If a star gives good evidence for close-up investigation, journeying there will need to be planned exquisitely with respect to where it will be. (As Art pointed out)

Click to view full size image

Good point, Ron!

Michael J. Fox, if you had a time machine that sent you back in time without sending you to the exact right point in space in the direction of Carina quite far away from "here", you would end up in empty space and freeze all the body parts off your body.

Ann

[Nitpicker]

I suppose the list of brightest stars is based on what is resolvable by the unaided eye. So, Alpha Cen is considered brighter than Arcturus.

The explanation referred specifically to “the brightest star in the Alpha Centauri system.”

Well, yes and no ... the explanation is perhaps not worded as well as it could be:

The brightest star in the Alpha Centauri system is quite similar to our Sun, has been known as long as recorded history, and is the third brightest star in the night sky.

Alpha Cen AB was first observed as a binary in 1689 (obviously well into the period of recorded history). So, while it is true that Alpha Cen A is similar to our Sun, it is Alpha Cen AB (considered as single source) that has been known since pre-historic times, and which is considered to be the third brightest star in the night sky.

[Ann]

Pace today's APOD, Proxima Centauri is not unusually faint. Its apparent magnitude is 11 and it can be seen in a small telescope. What was discovered in 1915 was its closeness to us rather than its existence.

John

Actually, I think that Proxima Centauri really is quite faint even as M-type dwarfs go. According to this page, the average mass of M-type dwarfs is 0.3 solar masses. But according to Wikipedia, the mass of Proxima Centauri is only 0.123 ± 0.006 solar masses. Mass is strongly correlated with luminosity in main sequence stars, like the Sun and Proxima, so that the more massive a star is, the brighter it is. Correspondingly, the less massive the star is, the fainter it is.

So we have reason to think that Proxima might be on the faint side even for red dwarf stars. It is reasonably bright to us - magnitude 11 - only because it is so close to us. Its absolute magnitude is 15.4, which is really quite faint.

Ann

[neufer]

Pace today's APOD, Proxima Centauri is not unusually faint. Its apparent magnitude is 11 and it can be seen in a small telescope. What was discovered in 1915 was its closeness to us rather than its existence.

It is reasonably bright to us - magnitude 11 - only because it is so close to us. Its absolute magnitude is 15.4, which is really quite faint.

And John clearly was talking about its reasonably bright apparent magnitude of 11 (and not its absolute magnitude of 15.4). What is not clear, however, is whether the APOD explanation was, in fact, referring to its dim absolute magnitude... in which case John probably doesn't have much of an argument.

[Ann]

And John clearly was talking about its reasonably bright apparent magnitude of 11 (and not its absolute magnitude of 15.4).

Good point, Art. John, I wasn't trying to criticize your observation that Proxima is well visible in many amateur telescopes.

But I do find it fascinating that the nearest star outside our solar system really is so faint, even as small red dwarfs go. It is of course another fascinating coincidence that the brightest component of the Alpha Centauri system really is so Sun-like. Stars like the Sun actually aren't all that common. When Wikipedia lists the nearest 56 stars and brown dwarfs, there are only two early G-type stars among them. One is the Sun, the other is Alpha Centauri Aa.

Ann

[neufer]

Proxima Centauri: The Closest Star

Explanation: Does the closest star to our Sun have planets?

Unobtanium

<<James Cameron's Avatar is set in the mid-22nd century, when humans are colonizing Pandora, a lush habitable moon of a gas giant in the Alpha Centauri star system, in order to mine the mineral unobtanium, a room-temperature superconductor. Unobtainium is any fictional, extremely rare, costly, or impossible material, or (less commonly) device needed to fulfill a given design for a given application. The properties of any particular unobtainium depend on the intended use. For example, a pulley made of unobtainium might be massless and frictionless; however, if used in a nuclear rocket, unobtainium would be light, strong at high temperatures, and resistant to radiation damage. The concept of unobtainium is often applied flippantly or humorously. For instance, unobtainium is described as being stronger than helium, and lighter than air.>>

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Upsidaisium

<<Bullwinkle receives a letter informing him that his uncle Dewlap has passed on, leaving him a mine located on Mt. Flatten. Captain Peter "Wrong Way" Peachfuzz has been sent to make sure Rocky and Bullwinkle find Mt. Flatten, as its ore, the anti-gravity metal Upsidaisium, is much sought after by the U.S. government. While under the guise of a pair of prospectors, Boris and Natasha manage to help Rocky and Bullwinkle locate Mt. Flatten, which floats high in the air due to the high amount of Upsidaisium within it. Once they reach the mountain, Boris and Natasha are joined by their intimidating superior, Mr. Big, who tells them that Pottsylvania also seeks Upsidaisium as a means to eliminate a traffic problem (by building cars with the anti-gravity ore). Eventually, thanks to Rocky's ingenuity, Mt. Flatten is transported to Washington D.C., and the Upsidaisium is put under lock and key by the government.>>

[b][color=#0000FF][size=125]Mt. Flatten: The expected location of the island of stability. (The dotted line is the line of beta stability.)[/size][/color][/b]

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Ununpentium: Uup

<<Ununpentium (Uup) is the name of a synthetic superheavy element in the periodic table that has the atomic number 115. Ununpentium is calculated to have some similar properties to its lighter homologues, nitrogen, phosphorus, arsenic, antimony, and bismuth.

Ununpentium is expected to be in the middle of an island of stability centered around copernicium (element 112) and flerovium (element 114): the reasons for the presence of this island are however still not well understood. Due to the expected high fission barriers, any nucleus within this island of stability exclusively decays by alpha decay and perhaps some electron capture and beta decay. Although the known isotopes of ununpentium do not actually have enough neutrons to be on the island of stability, they can be seen to approach the island as in general, the heavier isotopes are the longer-lived ones. Its most stable known isotope, ²⁸⁹Uup, has a half-life of 220 milliseconds.>>