Astronomy explainers for curious readers: follow the evidence behind planets, distant small bodies, changing stars, and gravitational microlensing. Written from an enthusiast’s perspective, with attention to what observations can and cannot establish.
An asymmetric transit has an ingress, egress or internal shape that fails to mirror the other side of the event. The cause may lie in the star, material around the planet, orbital motion or the measurement process. The shape is a clue to investigate, not a unique diagnosis. First define the expected symmetry A spherical … Read more
Transit duration variations measure changes in how long a planet takes to cross its star. Another planet can produce them by perturbing the orbit, including its orientation. A changing duration is therefore a possible dynamical clue, but it does not identify a hidden planet by itself. Define which duration was measured The full transit duration, … Read more
Transit timing variations, or TTVs, are departures of measured transit midpoints from a constant-period schedule. Gravitational interactions between planets can produce them, allowing astronomers to constrain planetary masses and sometimes infer a companion that does not transit. A late transit alone is not a planet discovery. Build the reference clock first For transit number E, … Read more
A white dwarf is supposed to be simple. After a Sun-like star runs out of nuclear fuel, sheds its outer layers, and leaves behind its compact core, the remaining object gradually cools. In many cases, astronomers can predict fairly well how much light that cooling stellar remnant should emit at different wavelengths. Then some white … Read more
A planet can spend billions of years circling its star in apparent stability. Then the star begins to die. For planets around Sun-like stars, this does not usually mean an immediate explosion. Instead, the star gradually exhausts the hydrogen fuel in its core, expands enormously, brightens, and becomes a red giant. That transformation can completely … Read more
A white dwarf may look like the quiet endpoint of a star’s life, but its spectrum can contain evidence of a planetary system that once surrounded it. Among the most useful clues are absorption lines produced by calcium. Calcium should not remain visible for long in the atmospheres of many white dwarfs. The enormous surface … Read more
A white dwarf may look like the quiet ending of a planetary system. The star has exhausted its nuclear fuel, shed much of its outer material, and collapsed into a dense stellar remnant roughly comparable in size to Earth. Any planets, asteroids, and comets that once orbited the original star have already survived a period … Read more
A white dwarf should have an extraordinarily simple atmosphere. Its immense gravity pulls heavier elements downward, leaving the visible surface dominated mainly by hydrogen or helium. Elements such as calcium, magnesium, iron, and silicon should disappear beneath the photosphere relatively quickly. Yet astronomers repeatedly find white dwarfs whose spectra contain exactly these elements. They call … Read more