NASA will place an artificial star in Earth’s orbit

There are various objects in Earth’s orbit, even natural celestial bodies, that are temporarily captured by the planet’s gravity. But the star was not there yet. Fortunately, it will be artificial, and the purpose of its placement is other than to illuminate the Earth.

Who watches the stars in the sky? Astronomers, of course. Are all stars normal? No, because thanks to technological advances, we can use lasers to illuminate artificial stars in the sky, which are used to calibrate optical devices. These are neither large objects like real stars, nor distant objects, but simply points (spots, to be precise) of light created at a distance of several tens of kilometers above the Earth’s surface.

Thanks to this, astronomers can largely eliminate the oscillations of the Earth’s atmosphere (look at hot asphalt from a distance in the summer and you will immediately understand what it means). Adaptive optics technology is incredibly advanced today and allows visual acuity from Earth similar to that seen from space telescopes. Of course, the latter still has an advantage because the atmosphere blocks certain wavelengths, including most infrared radiation, and no amount of technology will help here. However, without artificial stars, the largest telescopes on Earth (with a mirror diameter of several meters or more) would be severely limited and the progress of science would be hindered to the level it was at least a dozen or so years ago.

What else do astronomers need?

But now that we have lasers that project artificial stars, computers that analyze the image, and flexible mirrors that change shape up to a hundred times a second, what more do we need? Well, better artificial stars might be helpful, ones that aren’t in view, but are somewhere in the sky. It is not necessary to place them thousands of light-years away from us, because the effect of obstacles on the path of light from the star to the observer only becomes significant when the light rays enter the Earth’s atmosphere.

It is enough to place such a star in Earth’s orbit, above the layers of the atmosphere that cause the greatest disturbances. This is something NASA plans to do to help astronomers using existing telescopes, as well as those super telescopes expected to be launched in the next decade.

Landolt, an artificial star that will appear in the sky in 2029

Landolt is the name of the satellite that will enter Earth’s orbit, specifically geostationary orbit, at a distance of approximately 36 thousand kilometers above the surface of the planet. During the first year of operation, the satellite will maintain a fixed position over the Earth’s Western Hemisphere. It will be available to telescopes in North and South America, where most of them are located. The Landolt project is actually a project of students from George Mason University. The equipment will be built in cooperation with the US National Institute of Standards and Technology (NIST), and NASA will help build and launch the satellite.

Landolt will be equipped with lasers that can simulate a real star by shining a focused beam. Compared to artificial stars viewed today using projectors attached to telescopes, Landolt’s will be a star with parameters known very precisely. This includes brightness, which is expected to become crucial for calibrating ground-based telescopes. Today’s artificial stars help determine the degree of oscillations in the atmosphere, but they are not useful in evaluating changes in brightness.

By knowing how the atmosphere changes the brightness of starlight, astronomers will be able to correct observations of actual stars and measure the brightness. Accurate measurement of brightness is very important in astronomy, if only because this feature of celestial bodies allows, in addition to other knowledge, to correctly evaluate distances in space. From brightness we can also infer the size, temperature and chemical composition of the object, that is, the information that makes up the image and our idea of ​​the distant world. We are already very good at this, but we are still far from perfect, as evidenced by inconsistencies in measurements and errors made by astronomers in determining the true nature of distant objects.

Will everyone be able to see the artificial star?

The Landolt satellite won’t be a star that everyone will see. To do this, you will need a telescope, which astronomers have at their disposal. Landolt will be equipped with exactly eight lasers, which, depending on needs, will be directed to a specific observation site. Astronomers will compare the brightness of an artificial star in Earth’s orbit with the brightness of dozens of currently observed stars and obtain the appropriate correction factor.

Arlo Landolt, creator of astronomical standards. On the left in 1960, on the right in 2014, six years before his death. (Image: NOIRLab CC BY 4.0)

Today’s techniques use stars with known characteristics as reference light sources, but the accuracy of such calibrations is much weaker than what a new satellite will enable. It is worth adding here that the name of the mission and the satellite – Landolt, comes from the name of the astronomer to whom astronomers owe their lists of so-called standard stars, that is, typical stars.

Source: University of Florida, NASA, information. king