Alpha Centauri’s stars

When Tanno and Iguda visited the Alpha Centauri binary star system, they also stopped in at Proxima Centauri. That’s a red dwarf star, the nearest star to Earth. And we recently discovered it has an Earth-like planet orbiting it.

What would it be like to visit our nearest exoplanet??

This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.

Artist’s impression of Proxima Centauri-b

Image credit: ESO/M. Kornmesser

3D animation of Proxima Centauri-b: Have a close look at what the nearest known exoplanet might look like close up: you can drag this image around and zoom in!

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3D image credit: NASA Visualization Technology Applications and Development (VTAD)

This NASA/ESA Hubble Space Telescope image shows the binary star system Stein 2051 on October 1, 2013, consisting of the brighter, redder "A" component at lower right and the fainter, bluer "B" component near the centre, a white dwarf star. Because these stars are only 17 light-years away they appear to move in the sky relative to the much more distant background stars in several months of observations with Hubble. The wavy blue line traces this motion, due to their true motion relative to the Sun combined with the parallax due to the motion of Earth around the Sun. Stein 2051 B appeared to pass close enough to one of these background stars, labeled "source" that the light from the background star was bent due to the mass of the white dwarf. This colour image was made by combining images taken in two filters with Hubble's Wide Field Camera 3. Links: Einstein revisited Hubble measures deflection of starlight by a foreground Object Release on Hubblesite

Binary system Stein2051 proved Einstein right!

In this picture, the blue wavy line shows where the white dwarf star Stein2051B appeared to move across the sky in 2013. The movement is wavy because of the Earth orbiting around a circle.

Image credit: NASA, ESA, and K. Sahu (STScI)

This illustration reveals how the gravity of a white dwarf warps space and bends the light of a distant star behind it. White dwarfs are the burned-out remnants of normal stars. The NASA/ESA Hubble Space Telescope captured images of the dead star, called Stein 2051 B, as it passed in front of a background star. During the close alignment, Stein 2051 B deflected the starlight, which appeared offset by about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a 1€ coin from 2300 kilometres away. From this measurement, astronomers calculated that the white dwarf's mass is roughly 68 percent of the sun's mass. Stein 2051 B resides 17 light-years from Earth. The background star is about 5000 light-years away. The white dwarf is named for its discoverer, Dutch Roman Catholic priest and astronomer Johan Stein. Links: Einstein revisited Binary star system Stein 2051 (annotated) Release on Hubblesite

Stein2051B is quite close and the star labelled ‘source’ is very far away. ‘Source’ was seen to be in the wrong position when Stein2051B passed in front of it. This is because the gravity from Stein2051B stretched space a bit and made the light bend so ‘source’ appeared in the wrong place.

This bending of light was predicted by Albert Einstein’s theory of relativity, and seeing this star appear in the wrong place is good evidence for the theory to be correct.

Image credit: NASA, ESA, and A. Feild (STScI)

Activity

Balancing binaries. Systems with two or more stars in them have complicated orbits, because everything orbits around the ‘centre of mass’ of the whole system. With very different mass stars this can give the system a real wobble.

Both stars orbit a point that moves around the green circle.

Image credit: NASA Space Place

You can make a model of this by balancing a ruler on a pointy object, like in this picture

Both stars orbit a point that moves around the point of the pyramid.

Image credit: NASA Space Place

Make a model like this one, and see where you have to put the balance point for various different mass stars. Investigate if you can work out a rule for how far the balance point has to be along the ruler for different combinations of star masses.

TOP TIP: you don’t need your stars to be round! They’ll sit on the ruler better if they’re not. Maybe use piles of coins so you can easily compare the mass at each end.

You can go to the previous DeepSpace secret pages by clicking the places below.