What are Some Celestial Objects?

Celestial body refers to the existence form of matter in cosmic space. The accumulation of celestial bodies has formed research objects of various astronomical states. The cosmic matter that people see exists in various forms. Those who gather form the stars, those who diffuse form the nebula, and those who are extremely thin are called interstellar matter, including interstellar gas and interstellar dust. All these materials are collectively called celestial bodies. Artificial satellites, spacecraft, space laboratories, and various detectors launched into space by humans are called artificial celestial bodies. ^[1]

[tin t]

As in

Judging whether a certain substance is a celestial body can be summarized by "three looks": first, see if it is

A long time ago, as long as it was not cloudy, people could see the stars in the night sky. in

Celestial body

Observers on Earth to celestial bodies

The theory of celestial body rotation mainly discusses the movement of the celestial body's rotation axis in space and the interior of the body and the change of the rotation rate. Among them, the Earth's rotation theory has been discussed in great detail. The movement of the Earth's rotation axis inside the body forms a polar pole movement (see

Using the law of universal gravity to measure the mass M of a celestial body and the radius r or diameter d of the celestial body, the density of the celestial body can be obtained. That is, = M / V = M / (4 R / 3).

Celestial body

We stood on the earth and looked up at the stars, and saw the stars in the sky as if they were all far away from us. The stars are like gems set on a circular sky.

The actual stars are far away from us. What we see is their projection on the surface of this huge sphere. This imaginary sphere is called the celestial sphere, and its radius is infinite. And the earth hangs in the center of this celestial sphere.

The direction in which the stars move in the sky is not random, and the shape of the constellation does not change. The stars climbed from the horizon in the east, to the highest point (midday), and then sank to the west. It looks like the entire celestial sphere is orbiting the earth. I believe everyone understands that the earth is not the center of the universe, and stars do not orbit the earth. The stars rotate around us in the sky because of the illusion that the earth rotates, the celestial sphere itself will not move. When we are in the earth, we do not feel that we are turning, as if we saw the scenery outside the window moving backwards when we were on the train, but we did not feel that we were moving.

Coordinate system on the celestial sphere

In order to accurately describe the position of stars in the sky, astronomers have developed a coordinate system to indicate the position of stars on the celestial sphere. This coordinate system is very similar to the latitude and longitude coordinates commonly used on Earth.

This coordinate system divides the celestial sphere into declination and right ascension. The declination algorithm starts from the celestial equator and ends at the poles. The celestial equator is 0 degrees, north to the celestial pole is +90 degrees, and south to the celestial south pole is -90 degrees. The algorithm of the right ascension is special. Unlike the algorithm of the longitude of the earth (from -180 degrees to +180 degrees), the ascension is from 0 to 24 hours from the west to the east of the celestial equator. Like time, the right ascension can be divided into 60 minutes per hour, and each minute can be subdivided into 60 seconds. The starting point of the right ascension calculation is the vernal equinox, which is one of the two intersections of the celestial equator and the ecliptic (the other is the equinox).

Like a spinning gyro, the earth's rotation axis is not fixed in space, but rotates at a period of 26,000 years. This movement is called precession. Therefore, the positions of the vernal equinox and the north pole of the celestial sphere will also move very slowly. Therefore, when we use celestial coordinates to indicate the position of celestial bodies, we should also indicate which year's coordinates, such as 2000 AD.

The NEOCam detector is the core technology of a NASA space telescope project to monitor small-Earth objects

BEIJING. According to the NASA website, an infrared detector that can help NASA improve its ability to detect and track asteroids and comets has passed key design phase tests.

The probe, called the Near-Earth Astronomy Camera (NEOCam), met design specifications in tests that simulate deep-space ambient temperature and pressure conditions. The "NEO Camera" is the core equipment of a space asteroid exploration telescope project to be implemented in the future. Details of the detector's design and specifications will be published in the published Journal of Optical Engineering.

The probe will be part of a new plan announced by NASA, which will for the first time focus on identifying and capturing near-Earth asteroids and dragging them into space near Earth for astronauts Carry out research.

Lindley Johnson, executive director of NASA's Office of Near-Earth Objects, said: "The implementation of this probe project signals the innovation of NASA's Discovery Project and its Astrophysics Research and Analysis Project. The investment in technology will improve our ability to protect the earth in the future and cope with the risk of collisions with alien objects. "

The so-called near-Earth objects generally refer to asteroids or comets within 28 million miles (about 45 million kilometers) of the Earth's orbit. Asteroids don't glow by themselves, they can only reflect sunlight. Depending on how high the albedo of a small celestial body is to the sun, a small celestial body with a high reflective surface may look similar to the optical observation characteristics of a larger asteroid with a low reflective surface. As a result, such observations made in the optical band sometimes have significant errors.

Amy Mainzer, chief scientist of the NEOWISE project at NASA's Jet Propulsion Laboratory, co-author of the forthcoming paper, said: "The infrared detector is a powerful tool that can be used to analyze asteroids. And confirm. When you use an infrared detector to observe an asteroid, what you are observing is the infrared thermal radiation it emits, which will allow scientists to more accurately limit its size and even tell you something about its composition. information."

The main breakthrough of the NEOCam detector is to improve the stability and reliability of its performance, and significantly reduce its quality, so that it can be launched on board a satellite. Once launched, this space telescope will be positioned at a distance of 4 times the distance between the earth and the moon, where the device will monitor the small celestial bodies close to the space of the earth day and night without being affected by clouds or any other Factors.

The successful development of this device is the result of close collaboration between NASA's Jet Propulsion Laboratory and its scientific partner, the University of Rochester (responsible for equipment testing), and Tredi Imaging Technologies (development of the equipment).

Craig McMurtry of the University of Rochester said: "We are pleased to see that this new generation of detectors is far more sensitive than the previous generation of similar devices."

NASA's NEOWISE project is an extension of the previous WISE, the "Wide-range Infrared Survey Detector", which launched in December 2009 and scanned the entire sky twice in the infrared band. During this period it took images of 2.7 million celestial objects, from distant galaxies to asteroids and comets near Earth. NEOWISE has completed surveys of small objects, asteroids and comets in the solar system. New discoveries made during the mission include 21 comets, more than 34,000 asteroids, and 134 NEOs. ^[2]